In conventional computer memory, a sense amplifier is one of the elements that make up the circuitry on a semiconductor memory chip (integrated circuit). A sense amplifier is part of the read circuitry that is used when data is read from the memory; its role is to sense the low power signals from a bitline that represents a data bit (1 or 0) stored in a memory cell, and amplify the small voltage swing or margin to recognizable logic levels so the data can be interpreted properly by logic outside the memory. Typical sense-amplifier circuits consist of two to six (usually four) transistors. Generally, there is one sense amplifier for each column of memory cells, so there may be hundreds or thousands of identical sense amplifiers on a modern memory chip.
In conventional sense amplifiers, however, the sensing margin is degraded with technology scaling due to a decrease in supply voltage, an increase in process variation, and limited sensing current to prevent read disturbances. To combat these problems, designers have turned to tighter magnetic tunnel junction (MTJ) resistance (RL and RH) distributions, higher TMR, or novel bit-cell structures (e.g., separated read and write paths). Unfortunately, these solutions have their own problems, such as poor sense margins and slow speeds along with issues in manufacturing process variations that result in widely varying performance of the circuits. In general, the degradation in the sensing margin is overcome by using offset-canceling circuits. However, these circuits have an inherent performance degradation because of the use of a multi-stage sensing operation.
Accordingly, there is a need for systems, apparatus, and methods that improve upon conventional approaches including the improved methods, system and apparatus provided hereby.
The inventive features that are characteristic of the teachings, together with further features and advantages, are better understood from the detailed description and the accompanying figures. Each of the figures is provided for the purpose of illustration and description only, and does not limit the present teachings.